textproduct: Quad Cities

KEY MESSAGES

- Mostly cloudy skies will persist into the weekend with another round of showers moving in late tonight/Saturday mainly over much of eastern Iowa and northeast Missouri. More widespread precipitation chances increase towards the middle of next week when a larger, wetter system moves in.

- Temperatures will continue to be cooler than average into the weekend, moderating back to seasonable or even slightly above normal levels next week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 139 PM CDT Fri Sep 25 2026

The remaining light showers from this morning should continue to dissipate this afternoon as a mid-level ridge-riding shortwave impulse weakens with time. Low-level moisture will remain in place, keeping skies cloudy overall today. The 25.12z ILX RAOB sounding continues to show a thermal inversion around the 800-650 mb layer, which isn't quite as strong as it was at the same time yesterday, but with dry air in this layer reinforced by easterly flow, this suggests a trend to drier conditions this evening through the overnight hours. With a lack of instability, any activity this afternoon should remain just showers, with no thunderstorms expected. A mix of cloudy skies to the west and mostly clear skies to the east are expected tonight as the drier air builds. Where skies clear, mainly over northwest Illinois, overnight lows should dip to the upper 40s/lower 50s, with mid to upper 50s to the west where the clouds linger.

On Saturday, yet another mid-level shortwave will build in from the west, which will support likely chances (60-80%) of showers across our west. However, this precipitation will run into a wall of dry air over our eastern CWA near a building surface high pressure ridge over the Great Lakes, so it will be tough for these showers to expand eastward. This is shown nicely in the latest HREF ensemble mean for Pwat values, which shows a very tight gradient over our CWA, from 1.6-1.8 inches over southeast Iowa to nearly a full inch less over northwest Illinois. The expectation is for rain to build over areas west of the Mississippi River, but struggle to go any farther east. The 25.12z HREF ensemble PMM QPF values indicates rain totals around one to three-tenths of an inch are possible. Highs Saturday will remain cooler west of the Mississippi due to the rain and cloud cover and warmer to the east where more sunshine is expected, with highs in the lower 60s to near 70, respectively.

Spotty showers will continue Saturday night, mainly west of the Mississippi River, with lows in the middle to upper 50s for most locations.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 142 PM CDT Fri Sep 25 2026

Outside of some lingering showers in the morning over our western CWA, the aforementioned high pressure system will strengthen over the region. Partly to mostly sunny skies and southeasterly flow Monday should result in the return of upper 60s to lower 70s for high temperatures.

This period of dryness will come to an end mid-week as a larger system builds in sometime around late Tuesday/Wednesday. A longer wave trough, with models showing a strong tropical connection to the systems from the eastern Pacific and the Gulf, should translate through the area, although the exact onset/ending time of associated precipitation remains uncertain. This is pretty clearly shown from the LREF ensemble cluster analysis, which shows various depictions of the longer wave trough aloft. Some shows a large progressive trough sweeping across the central CONUS, while some show a slower cut-off low with multiple rounds of rains mid to late week. However, there remains a strong signal for abundant moisture with this system given the tropical connection, with Pwat values progged around 1.6 to 2 inches, which is quite high for late September. In fact, these values would be in excess of the 99th percentile for Pwats per the NAEFS climatological percentiles. NBM exceedance probabilities for one inch or more of rain for Tuesday night and Wednesday are around 50-70%, which is actually a pretty decent signal given we're talking several days out. Despite the uncertainty on the exact duration and magnitude of rainfall amounts, this signal appears supportive of heavy rainfall and perhaps a flash flooding threat, given wet antecedent conditions, so this mid-week system bears watching. With this, WPC does have much of our area in a Day 5 Slight Risk (level 2 of 4) in their latest excessive rainfall outlooks.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1238 PM CDT Fri Sep 25 2026

Messy aviation conditions to continue this afternoon, with a mix of VFR/MVFR/IFR ceilings over the area. IFR conditions appear confined largely to areas along the Mississippi River. Confidence in the latest TAF set is lower than usual, given that the forecast models have generally struggled to capture the ongoing low ceilings, although the RAP model seems to have the best handle overall. We've leaned heavily towards this model, which suggests these low ceilings to linger through much of the afternoon. Light rain showers, which has brought MVFR visibility reductions to most sites, are expected to continue near BRL before waning later this afternoon. Eventually, conditions should improve to VFR tonight as drier east flow helps to scour out low-level moisture. Another system looks to bring another round of rain showers late in the TAF period, mainly for CID and perhaps BRL.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.